1. Field of the Invention
The present invention relates to press-fit electrical contact terminals and methods of making the same and, more particularly, to improvements in the through-hole press-fit portion of such an electrical contact for securing the electrical terminal in the through hole of a circuit board and a method of making the same.
2. Description of the Prior Art
FIG. 18 shows, in cross section, the through-hole press-fit portion 64 (hereinafter "press-fit portion") of a conventional press-fit electrical contact terminal which consists of a pair of contact portions 62 and 62' and a bridge portion 63 for connecting the contact portions 62 and 62' to form a N-shaped cross section. The bridge portion 63 is formed with opposed V-shaped notches 60 and 61 having a height or depth greater than a half of the height or thickness of the press-fit portion 64. The contact portion 62 or 62' has a pair of corners 64 and 65 or 66 and 67 abutting against the wall 68a of a through hole 68 as shown in FIG. 19.
When such an electrical terminal is press fitted in the through hole 68, the four corners 64-67 abut against the wall 68a of the through hole 68, and the bridge portion 63 is deformed to absorb the compression force produced by the abutment.
However, since the depth of the notches 60 and 61 is greater than a half of the thickness of the press-fit portion, not only a large amount of labor is necessary to make the notches but also it has been impossible to make subminiature terminals useful for through holes having a diameter of 0.6 mm or less because of lack of the strength in a coining process.
In addition, the compression force due to the abutment against the through hole 68 is absorbed by the deformation of the bridge portion 63 so that the deformation concentrates on the bridge portion 63, limiting the flexibility. As a result, there is a demand for contact terminals useful for subminiature through holes.
Moreover, the deformation and the compression force change abruptly so that the cross sectional area of a through-hole press-fit portion hardly change, limiting the range in diameter of useful through holes and requiring a large press-fit force.